1. Field of Invention
The present invention relates to a paper feeder, and more particularly to a paper feeder that reduces the occupied space and simplifies the assembling procedure.
2. Related Art
Various types of printing and output devices, such as printers, scanners, copiers and multi-functional peripherals (MFPs), are now available in the market. In each of these devices, two rubber rollers, including a pickup roller and a feed roller, are used to pickup and feed papers. The paper is firstly picked up from a paper tray by the pickup roller, and then is fed by the feed roller to perform the prearranged task, and finally is conveyed outside the device. The power for the motion of the two rollers is provided by transmission elements, such as gear sets or a belt.
FIGS. 1 and 2 are side views of paper feeders in the prior art.
FIG. 1 is a side view of a paper feeder in the prior art having a lower roller. A feed roller 20 is disposed on one side a paper tray 12, and is connected to a pickup roller 10 with a transmission mechanism 11. The pickup roller 10 moves downward to the paper tray 12 to be in contact with a paper 13, such that the pickup roller 10 drives the paper 13 to move to the feed roller 20 along a tangential direction of the roller. A lower roller 30 is disposed under the feed roller 20, and the lower roller 30 is in contact with the feed roller 20 appropriately. Therefore, when the paper enters, it is blocked by the lower roller 30, such that the paper 13 is rolled by the feed roller 20 to pass through the two rollers.
FIG. 2 is a side view of a paper feeder in the prior art having a lower friction plate mechanism. Here, the lower roller 30 is replaced by a lower friction plate mechanism 40. The lower friction plate mechanism 40 includes a lower friction plate 41 in contact with the feed roller 20 appropriately, and an elastic mechanism 42 combined to a bottom surface 43 of the lower friction plate 41, so as to provide an elastic force perpendicular to a tangential direction of rolling.
The two types of paper feeders described above are disadvantageous in terms of the design cost and the lifetime. Therefore, Taiwan Patent No. 500,061 entitled “Paper Separation Device for Automatic Paper Feeding” filed on Aug. 21, 2002 adds an elastic element on one side of the friction plate, so as to provide an elastic force opposite to the tangential direction of the feed roller, such that the friction plate moves along a direction opposite to the tangential direction. Thus, the lifetime of the friction plate is increased, and the cost is reduced.
According to the solutions provided in the prior art or Taiwan Patent No. 500,061, a roller set including two or more rollers is required, or a friction plate mechanism has to be added to pickup, feed, and separate papers. Therefore, the shortcomings of the mechanism include the components are too complicated to assemble difficulty, and the components occupy too much space, to cause the mechanism is not light and thin enough. In addition, the elastic element described in Taiwan Patent No. 500,061 must provide an opposite elastic force according to the acting force of the feed roller. As the elastic element outputs the force linearly, the force output is influenced by the compression amount, while the compression force is easily influenced by the tolerance in assembling. Therefore, the design problem that the elastic force output is difficult to control will occur.
Furthermore, U.S. Pat. No. 6,499,736 entitled “Paper Feeder for Papers with Different Thickness” filed on Dec. 31, 2002 disclosed that a roller device is used to perform the pickup motion, and a torsional spring sliding in a sliding slot is used to provide driving forces to pick up papers with different thickness.
Though U.S. Pat. No. 6,499,736 simplifies the roller set to a single roller, but the torsional spring is similar to the elastic element of Taiwan Patent No. 500, 061, the torsional spring is still disposed under the roller. Though the assembling procedure is simplified slightly, but the space that the assembled device occupies is not reduced, which does not satisfy the market requirements of being slight, thin, and simple in design, and is not helpful to improve the competitiveness and convenience of the product.